Investigation of BiFeO₃-BaTiO₃ lead-free piezoelectric ceramics with nonstoichiometric bismuth

BiFeO₃-BaTiO₃ (BF-BT)-based lead-free ceramics are promising piezoelectric materials exhibiting high Curie temperatures and excellent electrochemical properties. In this study, 0.70Bi_1+xFeO₃-0.30BaTiO₃ (B_1+xF-BT, x =-0.01, 0.00, 0.01, 0.02, 0.03, 0.04) lead-free piezoelectric ceramics were successfully fabricated via the conventional solid-phase reaction process. Crystallographic structure, microstructure, dielectric, impedance, ferroelectric, and piezoelectric properties among different compositions were comprehensively investigated. The X-ray diffraction analysis confirmed that all compositions exhibited a typical perovskite structure with a cubic-rhombohedral phase mixture. The grain size of ceramics tends to increase as the Bi₂O₃ content rises. In particular, the backscattered electron images and energy dispersive analysis revealed prominent core-shell microstructure within grains. Notably, the BF-BT ceramic containing 1% excess Bi displayed the maximum d₃₃ ~217 pC/N and ~243 pm/V accompanied by a high Curie temperature of 515 °C. The findings demonstrate the potential feasibility of BF-BT ceramics in the field of lead-free piezoelectric ceramics.